The present invention relates generally to a housing for a sonic transducer and more particularly to a housing for an ultrasonic transducer utilized in a echo-ranging object detection system.
Sonic transducers, and particularly ultrasonic transducers, have been utilized in a variety of echo-ranging object detection systems. In a typical system, the transducer will transmit a sonic pattern into a surveillance area. If an object is present, the sonic pattern (wave form) will be reflected back to the transducer. That same transducer, or a second one, can then signal the perception of a sonic pattern to indicate the presence of the object in the surveillance area. The reception may be signalled based upon either the strength or upon the timing of the signal received.
A typical sonic, and particularly an ultrasonic, transducer produces a sonic pattern in the form of a primary lobe and a secondary lobe. The primary lobe is projected out in a primary direction and covers a certain area around that primary direction. A secondary lobe is projected at an angle to the primary direction surrounding the primary lobe. Since the secondary lobe is projected at an angle surrounding the primary lobe, the coverage of the combined sonic pattern will not be uniform at a given distance from the transducer. The combined sonic pattern will have a center coverage area formed by the projection of the primary lobe and a donut-shaped coverage area formed by the secondary lobe surrounding the center coverage area. There may be a space or area between these coverage areas which will not receive this sonic pattern.
The typical sonic transducer utilized in an echo-ranging object detection system would produce a non-uniform coverage. If an object is present in the surveillance area where the sonic pattern is impinging, it would provide a reflection of that sonic pattern. However, if an object were present in the surveillance area where the sonic pattern is not impinging, it cannot, of course, reflect the sonic pattern back to the sonic receiver. The sonic receiver may be either the same transducer as the projecting transducer or it may be a second transducer.
Further, the object may be present in the surveillance area where the sonic pattern impinges upon the object, but the object may be slightly angled with respect to the transducer such that it might reflect that sonic pattern, not exactly back to the transducer. This reflection would be missed by the receiving transducer without a suitable housing collecting or focusing the sonic pattern back to the receiving transducer.
One installation of an echo-ranging object detection system utilizing a transducer is a system to detect the presence of automobiles. A typical example would be a system to detect the presence of an automobile at a location not visible to an interested party. An example would be a drive-up ordering station (menu) at a fast food restaurant.
A typical problem at such installation is unwanted false returns. The false returns may be from ground clutter, such as pebbles on a roadway, from snowbanks, or from channelization curbs, for example. The echo-ranging object detection system in this type of installation should restrict the area of coverage in one zone or quadrant (typically the bottom quadrant), to shield out unwanted false returns.
An outdoor installation accessible to the public may also need to be physically protected. The system may be shielded from the elements to protect the transducer and other vulnerable parts of the system from rain, snow, sleet, etc. The system may also be shielded from unwarranted physical intrusion as by vandalism, blowing debris and small animals, for example.